Project Summary Rheumatoid arthritis (RA) affects up to 1-2% of the general population in North America. The cause of RA is still not fully understood but involves complicate interactions between genes and environment. As more effective therapies for RA are emerging, the focus of RA care is shifting from controlling inflammation to early detection, prevention, and cure of this disease. The ultimate goal of this project is to understand how the disease process of RA is initiated. Preliminary data of this study suggest that blood cells obtained from healthy first-degree relatives (FDRs) of RA patients already display several abnormal features that are also seen in untreated RA patients, indicating that those abnormal features predate the clinical symptoms of RA. The first aim of this project is to use biochemical approaches to characterize those abnormal features in blood cells from FDRs, and to establish a chronological and causal relationship among those features. The second aim is to use pharmacological and genetic approaches to examine how the cascade of the abnormal features is triggered and how one feature leads to the next. The final aim is to examining blood cells obtained from newly diagnosed RA patients before and after treatments in order to determine if effective RA treatment will mitigate these abnormal features. Taken together, this project will delineate a sequence of molecular events leading to the development of clinical symptoms of RA and will bring us one step closer to the initial trigger of RA.